Grit blasting machine and method

Abstract

A grit blasting machine which projects particles of metal grit, having at least a soft magnetic property, against a surface to be cleaned to remove scale therefrom. The machine includes a vehicle movable along the surface. A housing mounted on the vehicle has an opening facing the surface through which the grit is projected by a throwing wheel mounted within the housing. The grit is picked up by at least one endless belt formed from non-magnetic, magnetically permeable material. The belt is connected with the vehicle and driven peripherally along a closed path having a pickup region and a release region. A plurality of magnets positioned interiorly of the belt cause the grit to become attached to the belt in the pickup region and to be carried to the release region. As the grit on the belt reaches the release region of the path, the grit is separated from the belt and is collected and recirculated to the throwing wheel.

I claim: 
     
       1. A grit blasting machine for removing scale from a surface to be cleaned utilizing particles of metal grit susceptible to magnetic attraction, the grit blasting machine comprising: a vehicle adapted for motion along the surface in a forward direction extending longitudinally of the vehicle, said vehicle having forward and rear ends;   a housing having an opening facing the surface;   means for mounting said housing on the forward end of said vehicle with said opening positioned forwardly of said vehicle;   blasting means connected to said housing for projecting the grit through said opening against the surface to remove the scale therefrom;   at least one endless belt formed from non-magnetic, magnetically permeable material;   means connected with said vehicle for supporting said belt in an endless path and for driving said belt peripherally along said path, said path including, a pickup region facing toward the surface in spaced adjacent relation thereto, continued motion of said vehicle moving said pickup region successively over portions of the surface travelled over by said housing,   a release region;     magnetic means connected to said vehicle for magnetically attracting grit present on the surface facing said pickup region onto said belt and for holding the grit on said belt until the grit reaches said release region, the portions of said belt passing through said release region not being subjected to sufficient magnetic force to hold the grit on said belt by magnetic attraction; and   means for causing the grit to become separated from said belt during passage through said release region.   
     
     
       2. A grit blasting machine as defined in claim 1, further including: recirculating means connected to said vehicle receiving the grit separating from said belt in said release region for recirculating the grit to said blasting means.   
     
     
       3. A grit blasting machine as defined in claim 1, wherein said means for supporting and driving said belt includes: a frame connected to said vehicle;   a plurality of spaced, rollers generally parallel to the surface rotatably connected with said frame supporting said belt for peripheral motion along said path; and   means contacting said belt to drive it peripherally along said path.   
     
     
       4. A grit blasting machine as defined in claim 3, further including: adjustable supporting means connecting said frame to said vehicle for adjusting motion of said frame relative to said vehicle to selectively vary the spacing of said pickup region from the surface   
     
     
       5. A grit blasting machine as defined in claim 2, wherein the projection of the grit against the surface also causes the creation of airborne dust, the grit blasting machine further including: a hollow interior space within said vehicle open at its lower end thereof facing towards the surface, the interior of said housing communicating with said interior space of said vehicle, said belt being positioned within said interior space;   a flexible, resilient skirt extending peripherally around said vehicle into contact with the surface for preventing escape of dust, grit, and scale from said housing and from said interior space within said vehicle; and   suction means for applying suction to said interior space to withdraw the dust therefrom.   
     
     
       6. A grit blasting machine as defined in claim 2, further including, scale separating means connected with said recirculating means for separating detached scale from the grit before the grit is redelivered to said blasting means.   
     
     
       7. A grit blasting machine as defined in claim 6, wherein said scale separating means includes: a first screen connected with said recirculating means having a mesh size such that grit can pass through said first screen but scale particles larger than the grit particles are retained on said first screen; and   a second screen connected with said recirculating means downstream of said first screen, receiving the particles passing through said first screen, said second screen having a mesh size smaller than the particles of grit to cause the grit particles to be retained on said second screen wherein scale particles smaller than the mesh of said second screen pass therethrough, said recirculating means delivering the grit retained on said second screen to said blasting means.   
     
     
       8. A grit blasting machine as defined in claim 1, wherein said housing and said blasting means are connected together to form a unit, said unit being removably connected with said vehicle to enable said unit to be selectivelys removed and replaced with another such unit. 
     
     
       9. A grit blasting machine as defined in claim 1, further including: adjustable mounting means supporting said housing on said vehicle for limited, selectively adjustable motion in opposite, transverse directions relative to said vehicle.   
     
     
       10. A grit blasting machine as defined in claim 2, wherein said recirculating means includes: collecting means connected to said vehicle for collecting the grit separating from said belt in said release region;   a hopper connected to said vehicle spaced from said collecting means, said hoper having an opening for the passage of grit outwardly from said hopper;   a first conveyor connected to said vehicle for conveying grit from said collecting means to said hopper; and   a second conveyor connected to said vehicle positioned to receive the grit from said hopper opening for conveying the grit therefrom to said blasting means.   
     
     
       11. A grit blasting machine as defined in claim 10, wherein said second conveyor includes: a generally tubular conduit connected to said housing, said conduit communicating at one of its ends with said hopper opening and at its other end with said blasting means;   a screw conveyor mounted concentrically in said conduit for moving the grit along said conduit from said hopper to said blasting means; and   a tubular mesh screen in contact with the flights of said screw conveyor and spaced from the interior of said conduit, said tubular screen having a mesh size such that the grit is retained within said tubular screen while particles of smaller size than the grit pass outwardly through said tubular screen.   
     
     
       12. A grit blasting machine as defined in claim 10, further including: a hopper screen positioned between said first conveyor and said hopper, said hopper screen having a mesh size such that the grit can pass through the mesh into the hopper while particles larger than the grit are retained on said hopper screen.   
     
     
       13. A grit blasting machine as defined in claim 5, wherein said suction means includes: a suction pump mounted on said vehicle having a suction inlet and an outlet;   duct means connecting said suction inlet with said interior space in said vehicle for application of suction thereto; and   a movable dust collector releasably hitched to and towed by said vehicle, said dust collector connected to the outlet of said suction pump.   
     
     
       14. A grit blasting machine as defined in claim 1, wherein said housing includes: a vertically and laterally extending, generally rectangular enclosure provided with said opening at its lower end: and wherein said blasting means includes:     a throwing wheel mounted within said enclosure for rotation about a horizontal, longitudinally extending axis;   means for rotating said throwing wheel; and   an inlet duct extending through said enclosure for feeding grit against said throwing wheel to be flung centrifugally downwardly thereby against the surface.   
     
     
       15. A grit blasting machine as defined in claim 14 said mounting means including: a first supporting structure connected to said enclosure;   a second supporting structure connected to said vehicle in adjacent relation to said supporting structure connected to said enclosure;   bearing means connected to said supporting structures mounting said enclosure for transverse sliding motion relative to said vehicle; and   adjusting means connected to at least one of said supporting structures for selective transverse positioning of said enclosure relative to said vehicle.   
     
     
       16. A grit blasting machine as defined in claim 1 wherein said magnetic means includes: a plurality of permanent magnets connected to such vehicle positioned internally of said belt in close proximity thereto extending along said pickup region and from said pickup region to said release region.   
     
     
       17. A grit blasting machine as defined in claim 16 wherein at least one of said permanent magnets includes: a permanently magnetized roller rotatably mounted in said vehicle between said pickup region and said release region, said belt travelling at least partially around said permanently magnetized roller.   
     
     
       18. A grit blasting machine as defined in claim 1, wherein said means for separating the grit from said one belt includes; a second endless flexible belt formed from nonmagnetic, magnetically permeable material;   second means connected to said vehicle for supporting said belt in a second endless path and for driving said second belt peripherally along said second path, said second path including, a second pickup region facing towards said release region of said one belt in spaced adjacent relation thereto,   a second release region,     second magnetic means connected to said vehicle for magnetically attracting grit positioned on the release region of said one belt onto said second belt and for holding the grit on said second belt until the grit reaches said second release region, the portions of said second belt passing through said second release region not being subjected to sufficient magnetic force to hold the grit on said second belt by magnetic attraction.   
     
     
       19. A grit blasting machine as defined in claim 18, wherein, said one belt is configured as a generally horizontal, flattened first loop with said pickup and release regions constituted by vertically spaced, generally horizontal, lower and upper portions of the first loop, respectively; and   said second belt is configured as a generally horizontal, second flattened loop with said second pickup and said second release regions constituted by vertically spaced, generally horizontal, lower and upper portions of the second loop, respectively; the lower portion of the second loop at least partially overlapping the upper portion of the first loop.   
     
     
       20. A grip blasting machine as defined in claim 18, further including, a leading end of said second belt positioned in overlapping relation to said one belt, said second belt travelling around said leading end thereto in an upward direction from said second pickup region to said second release region, said second magnetic means retaining the grit on said second belt during passage through said second end;   a trailing end of said second belt spaced from said leading end extending beyond said one belt, said second belt travelling in a downward and generally circular path around said trailing end thereby causing the grit particles to become separated from said second belt; and   a collecting chamber extending partially around and beneath said trailing end of said second belt to collect the grit therefrom.   
     
     
       21. A grit blasting machine as defined in claim 20, wherein said second belt extends in generally perpendicular relation to said one belt. 
     
     
       22. A grit blasting machine as defined in claim 20, wherein said one belt travels peripherally in a direction extending transversely of he direction of movement of said vehicle and said second belt travels peripherally in a direction parallel to the direction of motion of said vehicle. 
     
     
       23. A grit blasting machine as defined in claim 20, further including: recirculating means connected to said vehicle for receiving the grit from said collecting chamber and redelivering it to said blasting means.   
     
     
       24. A grit blasting machine as defined in claim 19, wherein said magnetic means includes, a first permanent magnet fixedly connected to said vehicle positioned internally of said belt extending along and closely above the lower horizontal portion of the loop defined by said one belt;   a first roller of permanently magnetized material positioned internally of said one belt extending traversely thereof at the trailing end of said pickup region in the direction of peripheral travel of said belt; and wherein said second magnetic means includes,     a second permanent magnet fixedly connected to said vehicle positioned internally of said second belt extending along and closely above the lower horizontal portion of the loop defined by said second belt; and   a second roller of permanently magnetized material positioned internally of said second belt extending transversely thereof at the trailing end of said second pickup region in the direction of peripheral travel of said second belt.   
     
     
       25. A grit blasting machine as defined in claim 1, wherein said belt is flexible and wherein said means for supporting said belt includes: a pair of spaced, parallel supporting rollers positioned an equal distance from the surface, said belt contacting said supporting rollers on its inner surface and extending at least partially around said supporting rollers, the portion of said belt extending between said supporting rollers constituting said pickup region; and wherein said means for causing the grit to become separated from said belt includes,     at least one additional roller spaced from said rollers, said belt travelling over and at least partially around said additional roller, the portion of said belt passing around said additional roller constituting said release region.   
     
     
       26. A grit blasting machine as defined in claim 25, adapted for cleaning horizontal surfaces wherein, said supporting rollers support said belt generally horizontally in the pickup region in spaced adjacent relation to the surface,   said additional roller being spaced above said supporting roller in parallel relation thereto, said belt travelling downwardly and at least partially around said additional roller to cause the grit to separate from said belt under the combined influence of gravity and centrifugal force.   
     
     
       27. A grit blasting machine as defined in claim 26, further including, recirculating means connected to said vehicle positioned to collect the grit separating from said belt for recirculating the grit to said blasting means.   
     
     
       28. A grit blasting machine as defined in claim 25, wherein said magnetic means includes, a first permanent magnet fixedly connected to said vehicle positioned internally of said belt extending along and closely above said belt in said pickup region;   one of said supporting rollers positioned at the trailing end of said pickup region in the direction of peripheral motion of said belt being permanently magnetized; and   a second permanent magnet fixedly connected to said vehicle positioned internally of said belt extending from said one of said supporting rollers toward said additional roller.   
     
     
       29. A grit blasting machine as defined in claim 26, further including, first and second intermediate rollers rotatably connected with said vehicle in spaced parallel relation to said additional roller, said first and second intermediate rollers contacting the interior and exterior surfaces of said belt, respectively, on a level with the upper and lower surfaces of said additional roller thereby causing said belt to pass around said additional roller in a U-shaped configuration with the arms of the U extending horizontally.   
     
     
       30. A grit blasting machine for removing scale from a surface to be cleaned utilizing particles of metal grit susceptible to magnetic attraction, the grit blasting machine comprising: a vehicle adapted for motion along the surface;   a housing mounted on said vehicle having an opening facing the surface;   blasting means connected to said housing for projecting the grit through said opening against the surface to remove the scale therefrom;   a first, endless, flexible belt formed from nonmagnetic, magnetically permeable material;   first means connected to said vehicle for supporting said belt in an endless path and for driving said belt peripherally along said path, said path including: a pickup region facing towards the surface in spaced adjacent relation thereto, continued motion of said vehicle moving said pickup region successively over the portions of said surface travelled over by said housing,   a first release region;     first magnetic means connected to said vehicle for magnetically attracting grit lying on the surface facing said pickup region onto said first belt and for holding the grit on said first belt until the grit reaches said first release region, the portions of said first belt passing through said first release region not being subjected to sufficient magnetic force to hold the grit on said first belt by magnetic attraction;   a second endless belt formed from nonmagnetic, magnetically permeable material;   second means connected with said vehicle for supporting said second belt in an endless path and for driving said second belt peripherally along said second path, said second path including: a second pickup region facing towards said release region of said first belt in spaced adjacent relation thereto,   a second release region; and     second magnetic means connected to said vehicle for magnetically attracting grit positioned on said first belt in the first release region onto said second belt and for holding the grit on said second belt until the grit reaches said second release region, the portions of said second belt passing through said second release region not being subjected to sufficient magnetic force to hold the grit on said second belt by magnetic attraction.   
     
     
       31. A grit blasting machine las defined in claim 30, wherein said second means for supporting said second belt includes, means guiding said second belt in a downward circular arc through said second release region to cause the grit on said second belt to become separated therefrom; the grit blasting machine further including,     means connected with said vehicle for recirculating the grit separated from said second belt to said blasting means.   
     
     
       32. A grit blasting machine for remvoing scale form a surface to be cleaned untilizing particles fo metal grit susceptible to magnetic attraction, the grit blasting machine comprising: a vehicle adapted for forward motion in a longitudinal direction, along the surface;   a housing having a downward opening facing the surface;   traverse means mounting said housing on the forward end of said vehicle for selectively adjustable transverse motion of said housing relative to said vehicle; and   blasting means connected to said housing for projecting the grit downwardly through said opening against the surface to remove the scale therefrom.   
     
     
       33. A grit blasting machine as defined in claim 32, further including, a pair of driven endless articulated tracks supporting said vehicle for motion along the surface.   
     
     
       34. A grit blasting machine as defined in claim 32 further including, recovery means for recovering the grit projected against the surface, and for recirculating the grit to said blasting means.   
     
     
       35. A grit blasting machine as defined in claim 34, wherein said recovery means includes, magnetic means connected to said vehicle for picking up the grit from the surface by magnetic attraction; and   conveyor means connected to said vehicle for conveying the grit picked up by said magnetic means to said blasting means.   
     
     
       36. A grit blasting machine as defined in claim 32, wherein said vehicle is generally rectangular with said forward end extending generally transversely, said vehicle further including: a hollow interior space within said vehicle open at the lower end thereof facing towards the surface;   a flexible, resilient first skirt extending peripherally around said vehicle except along said forward end, said first skirt extending vertically into contact with the surface for preventing escape of dust, grit and scale from said interior space;   a flexible, resilient second skirt extending peripherally around said housing except along a transverse end thereof facing said forward end of said vehicle, said second skirt extending vertically into contact with the surface for preventing escape of dust, grit and scale from said interior space;   first and second expansible seal means extending between and connected to said vehicle and said housing at opposite transverse ends thereof for permitting transverse motion of said housing relative to said vehicle while preventing escape of dust, grit and scale from a region between said housing and said interior space.